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 <meta name="date" content="2004-01-22" />
 <title>SSIM</title>
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<h1>SSIM</h1>

<h2>&Uuml;bersicht</h2>
<b>Autor:</b> Lefungus<br />
<b>Version:</b> 0.23<br />
<b>Download:</b> <a href="http://www.avisynth.org/warpenterprises/" target="_blank">http://www.avisynth.org/warpenterprises/</a> / <a href="http://perso.wanadoo.fr/reservoir/dl/SSIMSrc-0.23.rar" target="_blank">Quellcode</a><br />
<b>Kategorie:</b> Videovergleich<br />
<b>Anforderungen:</b> YV12 Farbraum<br />
<hr>
<h2>Description</h2>
<p><font face="verdana, arial, helvetica" size="2">This filter has been created
following the ideas of <a href="http://www.cns.nyu.edu/~zwang/" target="_blank">Zhou
Wang</a>.<br>
It has been coded with the great help of Mfa, who worked on the core functions.<br>
<br>
For a given reference video and a given compressed video, it is meant to compute
a quality metric, based on perceived visual distortion. Unlike the well-known
PSNR measure, it's not purely mathematical, and should correlate much better
with human vision.<br>
Some examples can be found <a href="http://http://www.cns.nyu.edu/~zwang/files/research/quality_index/demo_lena.html" target="_blank">here</a>.<br>
A higher MSE (and so lower PSNR) should mean that the compressed clip is a worse
image but MSE and PSNR are flawed in this respect as numerous tests have shown.
However with SSIM, according to tests carried out on the VQEG dataset, a higher
Q (SSIM value) has a much better relation to the visual quality of the
compressed clip. Despite this, bear in mind the SSIM metric still isn't perfect.<br>
<br>
This filter is designed to compute an SSIM value by two methods, the original
one, and a &quot;enhanced&quot; one that weight these results by lumimasking. On
the todo list is to include the motion weighting.<br>
<br>
This filter has five parameters:<br>
</font>
<blockquote>
  <pre><font face="verdana,arial,helvetica" size="1">code:</font></pre>
  <hr>
  <pre>ssim(clip1,clip2,&quot;results.csv&quot;,&quot;averageSSIM.txt&quot;,lumimask=true)</pre>
  <hr>
</blockquote>
<font face="verdana, arial, helvetica" size="2"><br>
clip1 and clip2 are the reference clip and the compressed clip.<br>
results.csv is the file where obtained SSIM values will be written (this can be
easily read in excel or notepad for those unfamiliar with the comma separated
variables format)<br>
lumimasking switch between the two methods.<br>
<br>
When the video is closed, the filter will write a file named
&quot;averageSSIM.txt&quot; that will contain the global SSIM value.<br>
<br>
An SSIM value is between 0 and 1, 1 meaning perfect quality.<br>
<br>
To analyse locally the results, you could use the csv files, and manipulate data
in any excel-clone. Examples:<br>
<a href="http://perso.wanadoo.fr/reservoir/dl/ssim.png" target="_blank">codec A
vs codec B</a><br>
<a href="http://perso.wanadoo.fr/reservoir/dl/ssimlumi.png" target="_blank">codec
A with lumi option</a><br>
<br>
In the csv file, when lumimasking is activated, both SSIM values and its weigth
is written.<br>
<br>
<b>Nota:</b><br>
-If you use B frames under xvid, trim the first dummy frame of the xvid clip,
and the last frame of the original clip<br>
</font>
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